Book/Report

FZJ-2019-03226

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Tight-Binding-Korringa-Kohn-Rostoker-Methode und Grenzflächenreflektivität in magnetischen Schichtsystemen

Wildberger, K. (Corresponding author)FZJ*

1997
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/22259

Report No.: Juel-3463

Abstract: $\textbf{In the first part}$ of the report a new and efficient ab-initio method to calculate the electronic structure of layered systems in slab geometry and of surfaces and interfaces with exact halfspace geometry is presented. The concept of a repulsive reference system with non overlapping, spherical potentials is introduced allowing an exact transformation of the traditional KKR multiple scattering method into an ab-initio tight-binding method. With the help of the repulsive reference systema fast and efficient electronic structure method for layered systems is developed. Extensive tests and applications to physical systems demonstrate the accuracy andefficiency of the method. The required computing time scales only linearly with respect to the number of monolayers ("N-scaling"). Furthermore, the decimation technique is introduced to calculate the "surface Green's function" in an efficient way. Self-consistent calculations for systems with semi-infinite geometry are discussed.For the new method we use two synonymous names: tight-binding or screened Korringa-Kohn-Rostoker Green's function method for layered systems. $\textbf{In the second part}$ of the report interface reflectivities for magnetic layers are calculated. The reflection coefficient represents the key quantity to understand interlayer exchange coupling (IEC) and quantum well states (QWS). First we calculate magnetic coupling energies for Fe, Co and Ni bilayers in Cu(100) using a KKR Green's function method for planar defects. Based on the relevant bulk band structures, the behavior of the long- and short-oscillation period can be qualitatively explained. Next we investigate the influence of the quantized electronic structure on the coupling for magnetic layers of finite thickness. The spin-dependent reflection coefficient for the scattering of a Bloch wave at the interface of a non-magnetic and a magnetic layer is an important quantity for the understanding of the coupling. The finite thickness of the magnetic layer leads to strong oscillations in the reflection amplitude due to the quantized d-bandstructure of the magnetic layer. Therefore the QWS are strongly structured and exhibit resonance anomalies in the peak positions, in contrast to the behavior of infinitely thick layers. We demonstrate that the amplitude and position (binding energy) of the QWS are determined, respectively, by the complex reflection coefficient and by its phase factor. Finally we show that the coupling can be influenced strongly by magnetic adlayers. The reflectivity exhibits sharp resonance anomalies that can be explained by a simple phase model.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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